1 / 39

NON-MSSM EXTENSIONS OF THE STANDARD MODEL

NON-MSSM EXTENSIONS OF THE STANDARD MODEL. Beautiful prediction of the MSSM (with GUT normalization of the U(1) generator ). is the gauge coupling unification: the three measured gauge couplings evolved to higher energy scales with the MSSM renormalization group equations

hedwig
Download Presentation

NON-MSSM EXTENSIONS OF THE STANDARD MODEL

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. NON-MSSM EXTENSIONS OF THE STANDARD MODEL

  2. Beautiful prediction of the MSSM (with GUT normalization of the U(1) generator ) is the gauge coupling unification: the three measured gauge couplings evolved to higher energy scales with the MSSM renormalization group equations (almost) meet at one point

  3. A closer look at the gauge coupling unification

  4. Define Mgut by

  5. Superpartner mass mass dependence can be described (in LL approx) by a single effective parameter Tsusy

  6. For instance, for universal gaugino masses at the GUT scale How precise is the gauge coupling unification in the MSSM?

  7. Generically, unification of the gauge couplings is lost in non-MSSM extensions of the SM Secondly, MSSM is easily consistent with precision electroweak data; other extensions are strongly constrained by them. In addition, good dark matter candidate So, why there are discussed various supersymmetric and non-supersymmetric non-MSSM extensions of the Standard Model?

  8. Original motivation: little hierarchy problem of the MSSM Effective Higgs potential for EWSB in many extensions of the SM (including MSSM for moderate tan beta)

  9. MSSM: cancellations 1:100 in the Higgs potential Little hierarchy problem(if a problem!)can be solved if both the tree level and the higher order corrections to mH are comparable to the Z mass Except for some more complicated supersymmetric models, the original motivation fails in non-supersymmetric extensions of the SM because of a new type of tension, namely with precision electroweak data Adam Falkowski Steve King

  10. The impact of physics beyond the Standard Model on precision electroweak data can be studied in a model independent way by adding to the SM lagrangian higher dimension operators

  11. Results of the fits to precision data: for new tree –level and/or strongly interacting sector Generically, non-MSSM extensions of the SM give new tree level effects and/or contain new strongly interacting sector. Typically

  12. The precision electroweak data are a challenge for realistic extensions of the SM aiming to understand better the origin of the Fermi scale. Although, non-supersymmetric extensions of the SM do not solve the little hierarchy problem of the MSSM, they can naturally protect the Higgs potential to the same extent as MSSM and are considered for their theoretical attractiveness. MAIN LOSS: UNIFICATION

  13. An attractive idea: extra dimensions. Originally, gravity in extra dimensions (with a low fundamental Planck scale) have been used as new strong dynamics to cut-off the SM at 1 TeV. Gravity effects would then be seen at the LHC , with signatures depending on whether the extra dimensional space is flat or e.g. of the Randall- Sundrum type. But in conflict with with precision data unless the strong gravity sets on at 5 TeV or higher.

  14. Gauge – Higgs unification : gravity can be decoupled (no gravitational effects at low energies); Higgs doublet is identified as a component along the extra dimension of a gauge field; gauge invariance in extra dimensions protects the Higgs potential Deconstructed version of this idea gives Little Higgs models; in 4 d the Higgs scalar is a pseudo- Nambu-Goldstone boson of some spontaneously broken global symmetry A large set of recently proposed models , either in 4+n dim or in 4d, have the same underlying idea, linked by deconstruction.

  15. Extra dimensions/deconstruction and Higgless models: Unitarity protected by contributions from Kaluza-Klein modes of vector bosons

  16. Instructive example: 5 dim SU(n) gauge theory

  17. To identify A5 with Higgs doublet: • A5 must be in a fundamental, not adjoint • representation of SU(2) • the loop scalar potential must have a minimum • for non-vanishing VeV • the generated quartic coupling for A5 must • be large enough to get mh>114 GeV We need model building

  18. Note that all the massive modes of A5 are eaten by the massive KK modes of the gauge bosons; The only physical scalar left in the spectrum is the zero mode of A5

  19. A tree level potential for A5 is forbidden by 5d gauge symmetry, also on the fixed points, and only loop contributions will generate a potential for the Higgs, that will be non-local from the 5d point of view, and therefore FINITE To generate an effective potential with a negative effective mass squared parameter one needs new fermions in the bulk

  20. Experimental signatures • New fermions • Heavy replica of W, Z and • (but not for Higgsless • because they are fermio- • phobic; for Higgless one should • measure gauge bosons self- • couplings to see KK • contribution Details depend on the model

  21. SUMMARY MSSM has important virtues (gauge coupling unification ) However, there are attractive non-MSSM extensions of the SM that naturally solve the big hierarchy problem and merit experimental verification; The present models are fairly complicated and no specific model emerges and the leading competitor to MSSM

More Related